Mechanism of Concentration-Dependent Vesicle-Micelle Transition in Aqueous Mixture of Cationic and Anionic Surfactants

The phase behavior of aqueous mixed solution of cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium octylsulfate was studied focusing on the concentration-dependent vesicle-micelle transition. Dynamic light scattering measurements and freeze fracture TEM observations showed that the ph...

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Bibliographic Details
Published inJournal of Oleo Science Vol. 54; no. 8; pp. 443 - 451
Main Authors NAKANISHI, Hisanori, TSUCHIYA, Koji, OHKUBO, Takahiro, SAKAI, Hideki, ABE, Masahiko
Format Journal Article
LanguageEnglish
Japanese
Published Tokyo Japan Oil Chemists' Society 2005
Japan Science and Technology Agency
Subjects
electroconductivity
FF- TEM
FT- IR
micelle
mixed surfactant system
phase behavior
spontaneous vesicle
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Summary:The phase behavior of aqueous mixed solution of cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium octylsulfate was studied focusing on the concentration-dependent vesicle-micelle transition. Dynamic light scattering measurements and freeze fracture TEM observations showed that the phase transition occurs in two steps depending on the total surfactant concentration. Equilibrium vesicles (V) formed in dilute solution was shown to transform to micelles (M) through a micelle/ small unilamellar vesicle (M+V) coexisting state. The concentration at which the transition from V to M+V occurs on the SOS-rich side lies around the CMC of pure SOS (120 mM). Moreover, electroconductivity and FT-IR measurements revealed that the phase transition is accompanied by a decrease in the degree of counter ion dissociation from surfactant molecules. Based on these experimental findings, the cause of the phase transition was discussed.
ISSN:1345-8957
1347-3352
DOI:10.5650/jos.54.443